Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ef-fĕrus, a, um, adj., very wild, fierce, savage (poet. and post-class.; freq. in Verg.): proles, Lucr. 2, 604; cf. juventus, Verg. A. 8, 6: Dido, id. ib. 4, 642: Chimaera, id. ib. 7, 787: mens Caci, id. ib. 8, 205; cf.: vis animi, id. ib. 10, 898: corda, Val. Fl. 1, 798: ira, id. 5, 517: virtus Bebrycis, id. 2, 648: facta tyranni, Verg. A. 8, 484: facinus, Sen. Phoen. 264; Flor. 4, 12, 12; 4, 12, 48; Sen. Element. 1, 13, 4.